Inhaled corticosteroids cannot adequately protect children with asthma from high levels of air pollution and may actually exacerbate the effects of pollutants, caution investigators in a clinical study.
The authors found that both long-term and short-term exposures to pollution were associated with decreased lung function and increased airway hyperresponsiveness among 1003 children with asthma who were enrolled in a trial comparing budesonide (Pulmicort, AstraZeneca) with nedocromil (which has since been withdrawn from the US market) or placebo.
Significantly, children receiving either budesonide or nedocromil had a more pronounced worsening of airway responsiveness with exposure to carbon monoxide (CO) than the children who were assigned to placebo, report Despo Ierodiakonou, MD, PhD, from the University of Groningen, the Netherlands, and colleagues in an article published online July 14 in the Journal of Clinical Allergy and Immunology.
"The important point is that even though these kids do have relatively well controlled asthma on inhaled corticosteroids, they still aren't totally protected from the effects of air pollution, so they need to pay attention to alerts and perhaps limit outdoor activities when air quality is poor," coauthor Paul V. Williams, MD, clinical professor of pediatrics in the Division of Allergy at the University of Washington School of Medicine in Seattle, told Medscape Medical News.
The public health implications of the finding are that asthma controller medications cannot be assumed to provide adequate protection for children with asthma during days when there is heavy ambient air pollution, Dr Williams said.
The investigators looked at short- and long-term exposures to ozone, CO, nitrogen dioxide, and sulfur dioxide among children enrolled in the Childhood Asthma Management Program (CAMP) trial. They also examined the question of whether use of either budesonide or nedocromil could protect against the effects of pollution.
They found that average CO concentrations were associated with a decline in lung function, as measured by the percentage change in forced expiratory volume for 1 second (FEV1) after use of a bronchodilator (change per interquartile range, −0.33 [95% confidence interval (CI), −0.49 to −0.16] for same-day change in CO concentration and −0.41 [95% CI, −0.62 to −0.21] for 1-week average CO concentration).
Similarly, CO was associated with declines in forced vital capacity (FVC) both on same-day and 1-week average CO concentrations (−0.19 [95% CI, −0.25 to −0.07] and −0.25 [95% CI, −0.43 to −0.07], respectively).
In addition, 4-month CO concentration averages were also negatively associated with declines in the percentage of predicted FEV1 and FVC before the use of a rescue inhaler. Both 4-month average CO and ozone concentrations were negatively associated with the FEV1/FVC ratio (P < .05).
"The worsening of [airway responsiveness] with short-term exposure to CO was stronger for children receiving budesonide and nedocromil compared with placebo, a finding that needs further investigation," the authors write.
"This means use of controller medication may not protect asthmatic children from pollutant effects and may actually worsen the negative effects of some pollutants," coauthor Diane R. Gold, MD, MPH, from the Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, Massachusetts, said in a news release.
The investigators also found that 4-month average nitrogen dioxide concentrations were associated with reduced postbronchodilator FEV1 and FVC percentage predicted. In particular, long-term exposures to sulfur dioxide were associated with a 20% or greater decline in FEV1. In addition, the use of an inhaled corticosteroid was associated with a worsening of the effect of CO on FEV1.
"There is a lot of speculation on why we saw some of those changes, and some people thought that because children who use inhaled corticosteroids had better control of their asthma that they spent more time outdoors playing, but we don't really have any evidence for that," Dr Williams told Medscape Medical News.
The study was supported by the National Institutes of Health, the US Environmental Protection Agency, and the International Initiative for Environment and Public Health Cyprus Program of the Harvard School of Public Health. Dr. Williams reported receiving research support from the National Institutes of Health. Dr. Gold disclosed receiving research support from the US Environmental Protection Agency, the National Institutes of Health, and the International Initiative for Environment and Public Health Cyprus.
J Allergy Clin Immunol. Published online July 14, 2015. Abstract
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